Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA.
Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA.
Brain Behav. 2021 Mar;11(3):e02034. doi: 10.1002/brb3.2034. Epub 2021 Jan 13.
The orbitofrontal cortex (OFC) is involved in diverse cognitive and behavioral processes including incentive valuation, decision-making, and reinforcement learning. Anatomic and cytoarchitectonic studies divide the OFC along both medial-lateral and rostral-caudal axes. OFC regions diverge in structure and function, assessed in vivo using white matter tractography and blood oxygenation level-dependent (BOLD) MRI, respectively. However, interpretation of T *-weighted BOLD is limited by susceptibility artifacts in the inferior frontal lobes, with the spatial pattern of these artifacts frequently assuming the geometry of OFC organization. Here, we utilize a novel perfusion-weighted arterial spin labeling (ASL) functional connectivity approach, which is minimally susceptibility-weighted, to test the hypothesis that OFC topology reflects correlated temporal hemodynamic activity.
In healthy participants (n = 20; age = 29.5 ± 7.3), 3D ASL scans were acquired (TR/TE = 3,900/13 ms; spatial resolution = 3.8 mm isotropic). To evaluate reproducibility, follow-up scanning on a separate day was performed on a participant subset (n = 8). ASL-based connectivity was modeled for gray matter OFC voxels, and k-means clustering (k = 2-8) applied to correlation statistics.
These approaches revealed both medial-lateral and rostral-caudal OFC divisions, confirming our hypothesis. Longitudinal reproducibility testing revealed 84% voxel clustering agreement between sessions for the k = 2 solution.
To our knowledge, this constitutes the first in vivo cortical parcellation based on perfusion fluctuations. Our approach confirms functional OFC subdivisions predicted from anatomy using a less susceptibility-sensitive method than the conventional approach.
眶额皮层（OFC）参与多种认知和行为过程，包括激励评估、决策和强化学习。解剖学和细胞构筑学研究沿着内外侧和前后轴将 OFC 分开。OFC 区域在结构和功能上存在差异，分别通过白质束追踪和血氧水平依赖（BOLD）MRI 在体内进行评估。然而，T *-加权 BOLD 的解释受到下额叶的磁化率伪影的限制，这些伪影的空间模式通常假定为 OFC 组织的几何形状。在这里，我们利用一种新的灌注加权动脉自旋标记（ASL）功能连接方法，该方法对磁化率伪影的敏感性最小，以检验 OFC 拓扑反映相关时间血液动力学活动的假设。
在健康参与者（n=20；年龄=29.5±7.3）中，采集 3D ASL 扫描（TR/TE=3,900/13ms；空间分辨率=3.8mm 各向同性）。为了评估可重复性，在参与者子集（n=8）上进行了单独一天的后续扫描。对灰质 OFC 体素进行基于 ASL 的连接建模，并对相关统计数据应用 k-均值聚类（k=2-8）。
这些方法揭示了内外侧和前后侧 OFC 分区，证实了我们的假设。纵向可重复性测试显示，k=2 解的两次扫描之间有 84%的体素聚类一致性。
据我们所知，这是首次基于灌注波动进行的皮质分割。我们的方法使用比传统方法对磁化率伪影不敏感的方法证实了从解剖学预测的功能 OFC 细分。
